Yohimbe bark is most commonly taken because its active ingredient, yohimbine, is supposed to be an aphrodisiac. Yohimbe has been used in Africa in this way for hundreds of years, but there isn't any conclusive evidence suggesting the supplement works as a sexual stimulant. Yohimbe bark is actually considered unsafe in Germany because of its side effects, and the supplements available in the U.S. contain only small amounts (less than 7 percent) of the active ingredient [source: American Cancer Society].

What's interesting, though, is that some emerging evidence suggests that yohimbine may be effective in treating sexual dysfunction caused as a side effect of certain antidepressants, specifically selective-serotonin reuptake inhibitors (SSRIs) such as the popular brand name antidepressants Prozac, Paxil and Zoloft. Additionally, there is a possibility that yohimbine may also help treat some types of erectile dysfunction (ED) -- mild types caused by psychological rather than physical problems. In this regard, the American Urological Association is unconvinced of its efficacy and recommends further evaluation.